The main agents of the pharmacological activity of garlic (Allium sativum L.) are organosulfur compounds of which the most important one is allicin (diallylthiosulfinate). Allicin has a wide range of antibacterial and antifungal effects. It shows significant antioxidative and antitumor effect. Allicin is very unstable and depending on the external factors it is transformed into pharmacologically active derivatives. The most important are ajoenes and vinyldithiins. They take part in the inhibition of the thrombocyte aggregation, in the regulation of systolic and diastolic blood pressure, reduce the triglyceride and phospholipid levels and exhibit diuretic, antimicrobial, fibrinolytic and vasodilative effects. In exploring their stabilization, allicin complexes were synthesized with ?-cyclodextrin and urea as inclusion complexes. The results obtained in this dissertation present a scientific contribution to the research of new pharmacologically active compounds that might, in the near future, find significant application in the pharmaceutical industry.